Previous studies at the University of Illinois Temporomandibular Joint and Facial Pain Research Center have established a psychophysiologic basis for the Myofascial Pain-Dysfunction (MPD) syndrome. The present research program will continue to focus on the physiologic aspects of the disorder with particulr emphasis on the differences between pair on psychophysiologic origin (MPD) and that of organic etiology (TMJ). Among the methods to be used in studying the psychophysiologic parameters are signal detection theory and the measurement of evoked potentials. The pathological tissue changes in masticatory muscle, TMJs and related structures associated with the MPD and TMJ syndromes will be studied using histochemical, biochemical, immunochemical and microprobe x-ray analysis techniques. These findings will be correlated with improved radiographic (arthrography and tomography) examinations and clinical observation. Preliminary studies in normal animals and experimental models of pathological states will form the basis for the subsequent human investigations.